Search

Problems such as large data volumes, slow transmission rates and low security often occur when transmitting multiple digital images over the internet. In order to protect the content security of multiple images and improve the speed of internet transmission, a multi‐image encryption algorithm based on image hash, bit‐plane decomposition and dynamic DNA coding is proposed in this study. First, the proposed algorithm merges several grey images and image hashing algorithm is used to generate the initial key for chaotic mapping. Second, the random sequence generated by the improved three‐dimensional chaotic map is used to decompose the bit plane of the merged image and the bit‐plane matrix is substituted numerically. Finally, the random sequence generated by the four‐dimensional hyperchaotic system is used to perform dynamic DNA coding and calculation on the image and the final multiple ciphertext images are generated by decomposition of the pixel matrix. The experimental results show that the proposed algorithm has large key space, strong key sensitivity, strong security and robustness, and can resist various conventional attacks such as statistical analysis, differential attack, exhaustive attack, cropping and noise attack.

Herein, a catalytic self-deposition (CSD) strategy is proposed to build 3D magnetic porous carbon fibers with a complex helical/chiral structure (MHPFs) toward ultralight and low-frequency microwave absorption unprecedentedly. Different from energy-intensive chemical vapor deposition (CVD) method, the binary composition of cobalt-encapsulated carbon nanotube arrays (CNTAs) and hierarchical pore structure are manipulated by adjusting the CSD technology without exogenous carbon and reducing atmosphere. Micro-/nano-scale structures, 0D/1D integration effects, dielectric/magnetic loss mechanisms, and extraordinary 3D helical/chiral configuration endow MHPFs with remarkable microwave absorption properties. The minimum reflection loss (RLmin) of MHPFs-900 (900 stands for the carbonization temperature) at a low frequency (6.3 GHz) reaches astronomical −61.08 dB. The effective absorption bandwidth (EAB, RL

An anti-corrosion inhibitor is one of the most useful methods to prevent metal corrosion toward different media. In comparison with small molecular inhibitors, a polymeric inhibitor can integrate more adsorption groups and generate a synergetic effect, which has been widely used in industry and become a hot topic in academic research. Generally, both natural polymer-based inhibitors and synthetic polymeric inhibitors have been developed. Herein, we summarize the recent progress of polymeric inhibitors during the last decade, especially the structure design and application of synthetic polymeric inhibitor and related hybrid/composite.

Transition-metal chalcogenides (TMDs) are excellent lithium-ion battery electrode materials with high efficiency, high stability, and superior electrical conductivity. In this work, heterojunctions...

Chronic bacterial-infected wound healing/skin regeneration remains a challenge due to drug resistance and the poor quality of wound repair. The ideal strategy is combating bacterial infection, while facilitating satisfactory wound healing. However, the reported strategy hardly achieves these two goals simultaneously without the help of antibiotics or bioactive molecules. In this work, a two-dimensional (2D) Ti3C2Tx MXene with excellent conductivity, biocompatibility, and antibacterial ability was applied in developing multifunctional scaffolds (HPEM) for methicillin-resistant Staphylococcus aureus (MRSA)-infected wound healing. HPEM scaffolds were fabricated by the reaction between the poly(glycerol-ethylenimine), Ti3C2Tx MXene@polydopamine (MXene@PDA) nanosheets, and oxidized hyaluronic acid (HCHO). HPEM scaffolds presented multifunctional properties containing self-healing behavior, electrical conductivity, tissue-adhesive feature, antibacterial activity especially for MRSA resistant to many commonly used antibiotics (antibacterial efficiency was 99.03%), and rapid hemostatic capability. HPEM scaffolds enhanced the proliferation of normal skin cells with negligible toxicity. Additionally, HPEM scaffolds obviously accelerated the MRSA-infected wound healing (wound closure ratio was 96.31%) by efficient anti-inflammation effects, promoting cell proliferation, and the angiogenic process, stimulating granulation tissue formation, collagen deposition, vascular endothelial differentiation, and angiogenesis. This study indicates the important role of multifunctional 2D MXene@PDA nanosheets in infected wound healing. HPEM scaffolds with multifunctional properties provide a potential strategy for MRSA-infected wound healing/skin regeneration.

A copper-catalyzed tandem reaction has been developed for the synthesis of 1,2,3-triazole-fused indole derivatives. This protocol allowed us to access a wide range of 1,2,3-triazole-fused indole derivatives in moderate to excellent yields. The 1,2,3-triazole-fused indole derivatives emit blue and greenish light when excited at 365 nm. The products were further explored for their quantum efficiency and photophysical properties.

In this work, we design a novel ultra-light graphene/carbon nanofibers/carbon nanotube aerogels (GCNAs) with excellent thermal insulating and hot oil adsorption ability. The GCNAs is prepared by a facile freeze-drying method followed by post-carbonization treatment. The morphologies, compression property and oil adsorption ability of as-prepared GCNA at different temperatures are analyzed. The results show the density of GCNAs is below 3.2 mg/cm3 and present a stable porous morphology at 300 °C. Notably, the GCNAs shows high adsorption ratio (> 27300%) toward hot engine oil (200 °C). Finally, we demonstrate an application of as-prepared GCNAs to put out ethanol continuous spill fires. The ethanol was ignited immediately after being released from syringe needle. We observed that the spill fire growth with fuel spreading, and the transition to extinction. When we place GCNAs into the surrounding leakage site to stop the flow of oil, spill fire stop spread and steady in situ burning, because of the efficient adsorption of hot oil. We strongly believe that this GCNAs will provide a new promising way for the future controlling of oil-flowing fire in airplanes and avoid the possible secondary disaster.

In order to improve the key space of color image encryption algorithm, the sensitivity to the contents of plain images, the robustness against various types of known attacks, and to achieve the tamper location analysis, a novel color image encryption algorithm based on image hashing, six-dimensional (6D) hyperchaotic and dynamic DNA coding is proposed. Firstly, the color image is pre-processed and the hash sequence is extracted by image hashing algorithm which is used as the initial value and control parameter of chaotic system. Secondly, three color channels of the color image RGB are synthesized into a two-dimensional matrix and the pixels replacement are performed by using the improved two-dimensional chaotic map. Finally, a 6D hyperchaotic system is used to generate random sequences for DNA dynamic coding and arithmetic operations of color images, the encrypted image is obtained. The experimental results show that, compared with the existing methods, the proposed algorithm has a large enough key space, better plain-image sensitivity, better statistical and differential characteristics, as well as can resistant various forms of attacks such as noise and cropping, and the tampering image can be tamper-located analyzed, which has good security and strong robustness.

A transition metal-free aldol condensation/[1+2+3] annulation reaction of isocyanoacetates with 8-(alkynyl)-1-naphthaldehydes has been developed for the general synthesis of azafluoranthenes. This domino reaction enables successive formation of three new bonds and two rings from readily accessible starting materials in a single operation. Furthermore, this methodology can also be utilized to construct chromeno[4,3-c]pyridines and benzo[c][2,6]naphthyridines in moderate yields.

In order to control the relationship between the polymer structure and performance, multi-component reactions (MCRs) have been used to adjust the properties of polymers due to their high atom utilization and structural designability. As a newly emerging type of material, vitrimers combine the advantages of both thermoplastics and thermosets. Therefore, it would be an exciting idea if the advantages of MCRs can be used to prepare vitrimers. In this work, for the first time, the Ugi four-component reaction (Ugi-4CR) is utilized to fabricate polyamide vitrimers (Dx-Poly). Among the resultant Dx-Poly, D400-Poly exhibits the best mechanical properties (stress = 8.75 MPa and strain = 255%) as well as excellent reprocessing performance. Additionally, these materials also have self-healing and shape memory properties. The use of the Ugi-4CR to prepare polyamide vitrimers will not only expand the scope of application of MCRs to the materials field, but also offer new ideas for the preparation of structurally designable vitrimers, which makes the “old” organic reaction gain “new” vitality in the field of materials.

A metal-free approach has been developed for the synthesis of benzo[c]isoxazole (anthranils) containing 1,2,3-triazoles. The reaction proceeded efficiently through a [3 + 2] azide-alkyne cycloaddition, SNAr azidation and denitrogenative cyclization sequence. The metal-free protocol enabled effective construction of one N-O and three C-N bonds in one pot. In addition, the synthetic utility of the current methodology was further demonstrated by late stage modification of the obtained products.

Intrinsic self-healing elastomers capable of autonomously repairing structures and restoring functions upon damage have attracted significant attention. However, their mechanical properties tend to be poorer than those of similar common elastomers because of the low binding energies and poor interactions of dynamic motifs that confer good self-healing ability. The preparation of elastomers that combine autonomous self-healing ability and good mechanical properties remains challenging. In the present work, we have developed a facile and effective method to achieve mechanical toughening of polyacrylate elastomers by preparing an ABA tri-block copolymer without compromising self-healing performance using a multiphase design with different densities of physical crosslinks formed by carboxyl groups. An ABA tri-block acrylate copolymer with pre-designed A and B blocks was prepared via a two-step reversible addition–fragmentation chain transfer (RAFT) radical polymerization from commercially available monomers and subsequent acid hydrolysis. The resultant copolymer is transparent, and exhibits high fracture toughness (77.06 MJ m−3), high tensile strength (20.96 MPa) and good self-healing performance, with up to 93% of its original tensile strength and 83% of its original toughness after healing for 24 h at room temperature. This outstanding performance can be attributed to the novel multiple structural design, where the A blocks comprising polyacrylic acid (PAA) segments with high crosslink density maintain their macroscopic shape and provide the material with high mechanical strength, and the B blocks which are random copolymers of AA and n-butyl acrylate with sparse crosslinking dissipate energy to achieve exceptional mechanical toughening and enhance the mobility of molecular segments to promote autonomous self-healing ability via a dynamic breakage–recombination of hydrogen bonds. In addition, the as-prepared elastomer shows the characteristics of fluorescence emission, and exhibits shape memory behaviors.

Colorless polyimide (PI) films with outstanding mechanical and thermal properties are highly demanded in flexible electronics. Herein three 4,4′-diaminodiphenyl ether (ODA)-based diamines with different substituents (–CH3, –CF3) and substitution positions (ortho and meta positions) were synthesized. After reacting with a combination of 1,2,4,5-cyclohexanetetracarboxylic dianhydride (CHDA) and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) in a typical sequential reaction manner, four highly transparent copolyimide films with excellent mechanical strength, high heat-resistance and superior fracture toughness were fabricated. A copolyimide film made using m-3F-ODA exhibits a fairly high transmittance at 400 nm of up to 86.8%, tensile strength as high as 102 MPa, tensile modulus of 2.76 GPa and glass transition temperature above 308 °C. The desirable solubility enables the prepared PIs to be readily cast from solution into robust films. All these encouraging results make these PI films potential substrates in place of ultrathin glass in flexible displays.

Currently, polyimine vitrimer is restricted by unitary functionality and poor responsiveness to external stimuli, thus showing limited potentials for broader applications as a kind of smart materia...

Highly thermally conductive polyimide (PI) composites have great potential application in the heat-resistance electronic packaging field, but the poor interface between the PI matrix and fillers limits their application. Herein, we prepared the polydopamine (PDA) modified hexagonal boron nitride (h-BN@PDA)/polyimide (PI) composites by a simple “vacuum filtration - hot pressing” method. In this composite, the interfacial interaction between the PI matrix and h-BN micro-sheets was greatly enhanced after PDA modification, and a 2D-aligned structure was successfully constructed. In this work, the effect of PDA modification on the thermal conductivity, thermal stability and mechanical properties of PI composites was fully investigated. The thermal conductivity of the h-BN@PDA/PI composites rises as the modified filler increases, and reflects a distinct anisotropy on in-plane and through-plane direction. The highest in-plane thermal conductivity, 3.01 W m−1 K−1, is obtained in the 20 vol% h-BN@PDA modified for 6 h (h-BN@PDA(6h))/PI composite, about 1405% higher than pure PI sample, while its T10% reaches 525.2 °C, and the tensile strength and Young's modulus are still high, about 38.80 MPa and 8.33 GPa. Our study provides a feasible fabrication technology for the high-performance thermal management materials.

Herein, a novel dumbbell-like MnO/C microspheres with the yolk-shell structure, high monodispersity and regular morphology are successfully prepared by calcining precursors MnCO3/RF microspheres under the vacuum condition. The effects of calcination temperature on morphology, carbonization degrees of carbon shells and pore properties of MnO/C microspheres are systematically investigated. Benefited from the yolk-shell structure, reasonable distribution of MnO nanocrystals and porous structure, MnO/C microspheres prepared at 550 °C exhibit high reversible capacity of 852.6 mAh/g at 1.32C over 500 cycles, long-term cycling stability (888.4 mAh/g at 2.64C over 400 cycles) and excellent rate performance (454.39 mAh/g at 6.60C and 253.28 mAh/g at 13.20C are remained). Furthermore, the lithiation evolution of MnO/C microspheres in the long-term cycling process at nano- and micro-scales are revealed and the LiCoO2||MnO/C full cell present a great cyclic stability. Dumbbell-like MnO/C microspheres demonstrate potential applications for next-generation Li-ion batteries as anode materials profited from superior electrochemical performance.

An economical and highly uranium extraction from seawater remains a crucial task for energy sources and environmental safety. Aiming for improving the mass transfer rate of uranium from seawater, a new synthetic strategy was adopted to synthesize 2D-open channel microporous bio-adsorbent for uranium extraction from seawater. Herein, a vapor phase modification approach was adopted to graft divinylbenzene(DVB), and polyacrylonitrile(AN) onto the surfaces of microporous frameworks via a free radical polymerization method. The post-synthetic functionalization was carried out by hydrothermal process, where amidoxime groups are structure-directing agents to trap uranium. Further, amidoxime groups not only enhanced hydrophilicity but also adjusts adsorbents pKa. AO-Fc faces minimum interference of competing ions and achieves a high uranium adsorption capacity of 8.57±0.02 and 409±1 mg/g in seawater and simulated solution. Despite its stable structure, AO-Fc exhibits a long life span and negligible weight loss revealed AO-Fc could be applied as a potential adsorbent for radionuclides

Infantile neuronal ceroid lipofuscinosis (INCL), the most severe form of neuronal ceroid lipofuscinoses, is caused by mutations in the lysosomal enzyme palmitoyl protein thioesterase 1 (PPT1). Typical symptoms of this disease include progressive psychomotor developmental retardation, visual failure, seizures, and premature death. Here, we investigated seizure activity and relevant pathological changes in PPT1 knock-in mice (PPT1 KI). The behavior studies in this study demonstrated that PPT1 KI mice had no significant seizure activity until 7 months of age, and local field potentials also displayed epileptiform activity at the same age. The expressional levels of Iba-1 and CD68 demonstrated by Western blot analysis, the inflammatory cytokine TNFα content measured with enzyme-linked immunosorbent assay, and the branch number and length of microglia demonstrated by immunohistochemistry (IHC) were significantly increased at age of 7 months, all of which indicate microglia activation at an age of seizure onset. The increased expressional of GFAP was seen at an earlier age of 4 month and such an increase reached its peak at age of 6 month, indicating that astrocyte activation precedes microglia. The purinergic P2X7 receptor (P2X7R) is a ATP-sensitive ionic channel that is highly expressed in microglia and fundamental to microglial activation, proliferation, cytokines release and epilepsy. We show that the ATP concentration in hippocampal tissue in PPT1 KI mice was increased using an enhanced ATP assay kit and demonstrated that the antagonist of P2X7R, A-438079 significantly reduced seizures in PPT1 KI mice. In contrast to glial cell activation and proliferation, the significant reduction of synaptic proteins GABAAR were seen in PPT1 KI mice. These results indicate that seizure in PPT1 KI mice may be associated with microglial activation involving in ATP-sensitive-P2X7R signaling and damaged inhibitory neurotransmission.

BACKGROUND Both hydrocele and cryptorchidism are common congenital abnormalities with an increasing incidence in many countries. Testicular abnormalities such as testicular hydrocele and cryptorchidism and their relationship with maternal hyperglycemia have become current research topics. This study researches whether increased blood sugar levels lead to congenital testicular abnormalities. MATERIALS & METHODS This retrospective and consecutive cohort study was conducted on singleton pregnancies having completed 20 or more weeks of gestation from the Fujian Provincial Maternity and Children’s Hospital, China. Differences were assessed with the Pearson χ2 test and the t-test for categorical and continuous variables, respectively. Univariate and multivariate logistic analyses were applied for outcomes. RESULTS A total of 37375 infants were enrolled for the selection of cases and controls. We found that oral glucose tolerance test(OGTT) of the case group's glucose level dramatically increased compared with the control group at 1 hour and 2 hours (p = 0.001, p = 0.016). In the testicular hydrocele group a remarkable increase was observed inOGTT1H and OGTT2H with the same criteria compared to the control group (p = 0.0001). Moreover, mothers were diagnosed with gestational diabetes mellitus(GDM) at a higher rate (p = 0.0001). The prevalence of premature delivery was also significantly higher in the testicular hydrocele group than in the control group (p = 0.0001). However, the OGTT0H was significantly higher in the cryptorchidism group compared to the control group (p = 0.0257). CONCLUSION The present study showed that hyperglycemia during pregnancy leads to a higher prevalence of testicular abnormality of the infants, such as testicular hydrocele and cryptorchidism. However, further investigation is required to determine whether premature delivery and GDM could contribute to the observed conditions.

The preferred alkane carbon number (PACN) in the normalized hydrophilic-lipophilic deviation (HLD

The intrinsic sluggish kinetics of the oxygen evolution reaction (OER) limit the improvement of hydrogen evolution reaction (HER) performance, and substituting the anodic oxidation of biomass materials is an alternative approach, given its lower oxidation potential and higher added value compared to those of OER. In this study, a Ni

An economical and highly uranium extraction from seawater remains a crucial task for energy sources and environmental safety. Aiming for improving mass transfer rate of uranium adsorption from seawater, a new synthetic strategy was adopted for the fabrication of 2D-open channel microporous bio-adsorbent for uranium extraction from seawater. Herein, the in-situ ATRP grafting approach was adopted to graft divinylbenzene, polyacrylonitrile onto the surfaces of microporous frameworks via the vapour phase method. The post-synthetic functionalization was carried out by hydrothermal method, where amidoxime groups are structure-directing agents to trap uranium. Further, amidoxime groups not only enhanced hydrophilicity but also adjusts adsorbents pKa. AO-Fc faces minimum interference of competing ions and achieves a high uranium adsorption capacity of 8.57±0.02 and 409±1 mg/g in seawater and simulated solution. Despite its stable structure, AO-Fc exhibits a long life span and negligible weight loss revealed AO-Fc could be applied as a potential adsorbent for radionuclide.

Palmitoylation is a reversible and dynamic process involving addition of palmitic acid to cysteine residues of proteins. Studies have indicated that a variety of neuronal receptors, including glutamate receptors such as AMPAR, NMDAR, and GABAAR, are palmitoylated, which contributes to the dynamic modulation of synaptic strength in response to neuronal activity. However, little is known about the depalmitoylation of these receptors. In this study, we adopted PPT1-deficient mice, an animal model that closely mimics human disease of infantile neuronal ceroid lipofuscinosis (INCLs), by knocking in a CLN1 c.451C > T nonsense mutation. We identified for the first time that the GABAARα1 subunit rather than AMPAR is the substrate of PPT1. In PPT1-deficient mice, we found the excessive palmitoylation and extended membrane location of GABAAR. Miniature inhibitory postsynaptic current (mIPSC) recorded from CA1 pyramidal neurons of PPT1-KI mice was also enhanced without disturbance of excitatory neuronal transmission. Spatial learning and memory deficits with enhancement of γ oscillation while attenuation of phase coupling was shown in the mice at as early as 2-month-old. Application of N-tert-butylhydroxylamine hydrochloride, a thioesterase mimetic, attenuated PPT1 mutation-induced GABAAR hyperpalmitoylation and its membrane accumulation with improved neuronal transmission and memory functions in the mice. These data provide new insights into the mechanisms of neuronal disorder caused by depalmitoylation deficiency and offer a clue for further intervention for INCLs and other neurodegenerative diseases.

A novel metal-free, efficient cascade reaction has been developed to construct 1,2,3-triazole-fused 1,4-diazepinone skeletons. Mechanism investigation indicated that sodium azide has not only served as a 1,3-dipoles synthon in [3 + 2] cycloaddition but also prompted C-N bond formation. Furthermore, the potential utility of this protocol was demonstrated by scale-up synthesis of 1,2,3-triazole-fused diazepinone derivatives and the derivatization of them.

In order to solve the problems of poor security and small application scope of speech content authentication, and to improve the robustness, discrimination and real-time performance of speech authentication, a multi-format speech BioHashing algorithm based on energy to zero ratio and improved linear prediction minimum mean square error (LP-MMSE) parameter fusion is proposed. Firstly, the algorithm extracts the short-term logarithmic energy, zero-crossing rate and the covariance method’s LP-MMSE of speech signal to be processed. Then, the time-frequency parameters are fused, and the fused feature vector and the orthogonal normalized random matrix of the key control are generated into BioHashing sequences through the inner product form. Finally, the BioHashing is encrypted by equal-length scrambling using henon chaotic map. The experimental results show that the proposed algorithm not only has the characteristics of good discrimination, strong robustness, good security, high real-time performance and wide application range, but also realizes the detection and localization of small-scale tampering of speech through minimum code distance (MCD) algorithm. At the same time, the algorithm also validates the unidirectionality of BioHashing with trapdoor by comparative difference method.

In this work, we report the remarkable catalytic effects of a novel Ti3C2 MXene-based catalyst (Ni@Ti-MX), which was prepared via self-assembling of Ni nanoparticles onto the surface of exfoliated Ti3C2 nanosheets. The resultant Ni@Ti-MX catalyst, characterized by ultradispersed Ni nanoparticles being anchored on the monolayer Ti3C2 flakes, was introduced into MgH2 through ball milling. In situ transmission electron microscopy (TEM) analysis revealed that a synergetic catalytic effect of multiphase components (Mg2Ni, TiO2, metallic Ti, etc.) derived in the MgH2 + Ni@Ti-MX composite exhibits remarkable improvements in the hydrogen sorption kinetics of MgH2. In particular, the MgH2 + Ni@Ti-MX composite can absorb 5.4 wt % H2 in 25 s at 125 °C and release 5.2 wt % H2 in 15 min at 250 °C. Interestingly, it can uptake 4 wt % H2 in 5 h even at room temperature. Furthermore, the dehydrogenation peak temperature of the MgH2 + Ni@Ti-MX composite is about 221 °C, which is 50 and 122 °C lower than that of MgH2 + Ti-MX and MgH2, respectively. The excellent hydrogen sorption properties of the MgH2 + Ni@Ti-MX composite are primarily attributed to the peculiar core-shell nanostructured MgH2@Mg2NiH4 hybrid materials and the interfacial coupling effects from different catalyst-matrix interfaces. The results obtained in this study demonstrate that using self-assembling of transition-metal elements on two-dimensional (2D) materials as a catalyst is a promising approach to enhance the hydrogen storage properties of MgH2.

A new type of microwave absorbing material (TCF@Fe3O4@NCLs) with multi-layer heterostructure is designed and fabricated via a one-step pyrolysis process of the precursor (PF@Fe3O4@PDA). PF@Fe3O4@PDA is prepared by the technology of confined self-polycondensation, solvothermal method coupled with polymerization of dopamine (DA). The as-obtained material has the structure of tubular carbon nanofibers (TCF) embedded with Fe3O4 nanoparticles, dispersed Fe3O4 nanoparticles, and nitrogen-doped carbon layers (NCLs) from inside to outside. Notably, tubular carbon nanofibers provide the major dielectric loss. Fe3O4 nanoparticles significantly improve the microwave absorption ability at low frequencies and provide appropriate magnetic loss. NCLs improve the conductivity and facilitate the generation of multiple polarization effects, resulting in enhanced dielectric loss. The absorption mechanism is further elucidated. Based on the synergistic effect of double dielectric/magnetic loss composite materials, the interface introduced by multi-layer heterostructure, and conductive networks, TCF@Fe3O4@NCLs exhibits excellent reflection loss (RL) of −43.6 dB and effective absorption bandwidth (EBA) of 4.6 GHz (8.2–12.8 GHz) with a loading of 10%. The results demonstrate potentially promising prospects of TCF@Fe3O4@NCLs as new material candidate for microwave absorption.

NaAlH4 is one of the most promising hydrogen storage materials due to its high energy density. However, the sluggish kinetic hindered it stepping into practical application. In this work, a bottom-up strategy was employed to confine NaAlH4 between graphene nanosheets with a millefeuille-liked multi-layer morphology. The NaAlH4 particles were uniformly arranged between graphene layers, with a high loading up to 90%, and performed improved dehydrogenation kinetic. The dehydrogenation peak temperature 55.7 °C decreased comparing with commercial NaAlH4. The generality of this nano-structuring strategy were confirmed by the successful synthesis of TiO2–NaAlH4 co-confined composites as well as the further enhanced kinetic.

A growing number of core–shell structured microwave absorbents have been reported; nevertheless, there are few studies accessible about one-dimensional core–shell electromagnetic nanocomposites as microwave absorption materials. In this work, we have developed two kinds of novel electromagnetic nanocomposites, namely yolk–shell Fe3O4@void@SiO2 nanochains and Fe3O4@void@SiO2@PPy nanochains. Their components and morphologies have been characterized by X-ray diffraction (XRD), X-ray photoelectron spectra, scanning electron microscope and transmission electron microscope. The N2 adsorption–desorption isotherms have demonstrated their specific surface areas and porosity, and the magnetic properties have been recorded by the vibrating sample magnetometer. Investigation of microwave absorbing properties manifests that Fe3O4@void@SiO2@PPy nanochains have stronger absorption capability and broader effective absorption bandwidth than Fe3O4@void@SiO2 nanochains, which is caused by the introduction of polypyrrole shells, giving rise to the addition of conductive loss and the enhancement of dipole polarizations, interfacial polarizations, multiple reflection and absorption. Specifically, the minimum reflection loss value is − 54.2 dB (17.70 GHz) and the maximum effective absorption bandwidth can reach 5.90 GHz (11.49–17.39 GHz); thus, Fe3O4@void@SiO2@PPy nanochains will become promising microwave absorption candidates. This research once more demonstrates that necklace-like core–shell magnetic–dielectric complex benefit to enhancement of microwave absorption performance, and establishes a good foundation for exploiting the high-effective microwave absorbing materials.

The connectivity probability analysis of vehicular networks can be employed for providing theoretical guidance for both obtaining an accurate real-time traffic information and reducing hazardous traffic situations. Most previous studies focused on analyzing the connectivity probability of vehicular networks in physical (PHY) layer protocol. However, the effects of packet collision in media access control (MAC) layer on the connectivity probability of vehicular networks have been rarely studied, where MAC and PHY layers actually interact on each other. In this paper, some parameters are dynamically set and analyzed under consideration of the influence of MAC and PHY layers on the connectivity probability of vehicular networks. Numerical results are shown to be consistent with the proposed theoretical analysis.

In this paper, a three-step method has been applied for preparation of Fe/Fe3O4@TCNFs@TiO2 magnetic hybrid nanofibers (MHNFs) with three-layer core-shell structure. Firstly, tubular polymer nanofiber precursors with FeCl3 embedded in axis (TPNFPs) are synthesized by a confined self-condensation system developed earlier. After high-temperature conversion, tubular magnetic carbon nanofibers loaded with Fe nanoparticles inside (Fe@TCNFs) are obtained. Finally, TiO2 shell formation procedure is carried out by the hydrolysis of tetrabutyl titanate, and MHNFs with different TiO2 loadings are successfully fabricated. This material possesses both magnetic and dielectric loss abilities that shows excellent microwave absorbing performance. Under filler content of 15 wt%, the minimum reflection loss reaches −44.8 dB@13.9 GHz, and the absorbing layer thickness is only 1.6 mm. In addition, the electromagnetic parameters of MHNFs can be regulated and optimized by adjusting TiO2 loading. It brings better impedance matching property and improves microwave absorbing performance. Meanwhile, the composition, structure and electromagnetic parameters of MHNFs are systematically analyzed. The microwave attenuation mechanism is revealed. This study has guiding significance for the performance optimization of existing microwave absorbers.

The pore-size effect on ethane adsorption and ethane/ethylene separation in three isostructural metal azolate frameworks (MAF-123-Mn/Zn/Cu) were thoroughly investigated. MAF-123-Mn/Zn/Cu were synth...

Developing heterogeneous catalysts for hydrogenation under mild conditions is industrially significant, but there still remain some challenges in the preparation of inexpensive and highly active ca...

In order to solve the security problem of speech perception hash authentication, the application scope of speech authentication algorithm, and improve the robustness, discrimination and real-time authentication in the process of authentication, a multi-format speech BioHashing algorithm based on spectrogram is proposed. Firstly, the speech signal to be processed is converted into spectrogram and feature extraction is carried out by two-dimensional discrete cosine transform. Then, the dimensionality of the eigenvector is reduced by non-negative matrix factorization, and generation of BioHashing sequences by inner product of reduced dimension eigenvectors and orthogonal normalized random matrices. Finally, the BioHashing is encrypted by equal-length scrambling using Henon chaotic map. The algorithm also validates the unidirectionality of BioHashing with trapdoor by comparative difference method. The experimental results show that the proposed algorithm has the characteristics of good security, strong robustness, high real-time performance and wide application range.

Carbon nanomaterials with a hollow tubular nanofiber structure is of great interest for uranium­(VI) adsorption from water. Their unique structure not only exposes a good number of functional groups and high surface area but also shows quick ion transport capacity. However, finding a simple method to prepare a new carbon structure is challenging. Herein, a new tubular hyper-cross-linked polymer is fabricated in a single pot using α,α′-dichloro-p-xylene (DCX) as a monomer. After carbonization, hollow tubular nanofibers (HTnFs) are obtained. Further, HTnFs are modified with carboxylic (COOH) and sulfonic­(SO3H) groups to obtain HTnF-SO3H and HTnF-COOH designed for ultrafast and high uranium­(VI) adsorption from water. From the batch studies, uranium­(VI) adsorption efficiencies of two adsorbents are greater than 90 ± 0.5% under seawater conditions over a short period of 10 min. The accurate data fitting was performed by using different models and the adsorption results are in agreement with the Langmuir model. The adsorption results showing the maximum adsorption capacities of HTnF-COOH and HTnF-SO3H are 1928.59 and 1827.57 mg/g. The easy preparation, highest uranium­(VI) adsorption, and regeneration properties suggest that these adsorbents act as good uranium­(VI) adsorbents from large-scale water.

A low-cost and efficient material is highly attractive for the removal of radioactive metal ions from aqueous solutions. However, it is highly required and still challenging. In this work, novel bi...

In recent years, ionic liquids (ILs) have received increasing attention because of low vapor pressure, environment friendliness, good thermal and chemical stability and strong solubility. However, the liquid nature and high viscosity restrict their applications in some fields. Encapsulation of ILs is an attractive way to handle them easily. Herein, we proposed a facile method to prepare IL-loaded microcapsules using IL-in-oil emulsion as template, poly(amide-thioether) as surfactant and interfacial thiol–isocyanate click reaction for shell formation. In this system, core materials ILs were proved to be able to catalyze thiol–isocyanate reaction without side products, which significantly simplified the preparation process of microcapsules. The shell of the microcapsules was composed of polythiourethane and poly(amide-thioether), which provided a strong protection for ILs. In addition, compared with IL-in-water emulsion, the application of IL-in-oil emulsion avoided the side reactions of the highly active isocyanate. The IL content of the resulted microcapsules could reach as high as 70 wt.%. It was also demonstrated that the proposed encapsulation technology was suitable for ILs with different polarities. This work provides an efficient way to encapsulate ILs using emulsion template, which will make ILs find widespread applications across various fields.

Highly efficient Hg(II) adsorption from wastewater remains a crucial task for human health and environment protection. In present work, a simple method was used to develop a carbon-based mercury magnetic “trap” (magnetic sulphonated tubular trap, MSTT) as proved by increasing surface area and wide diameter porous magnetic trap with a high density of strong Hg(II) chelating groups. Various parameters including the initial concentration of Hg(II), pH, contact time and adsorbent dosage are analyzed. The adsorption results of MSTT and sulphonated tubular trap (STT) are closely fitted with the Langmuir adsorption isotherm with maximum adsorption capacities were 970.87 (mg/g) and 952.38 (mg/g). It reveals 99.9 ± 0.5% Hg(II) adsorption occurs at pH 6.8, which is close to neutral pH. These traps can efficiently reduce Hg(II) from 10 (mg/L) to 0.3 (μg/L) in a short time of 10 min. This level is lower than the permissible limit for the drinking water. The calculated thermodynamic parameters ΔH°, ΔG°, and ΔS° indicate that the adsorption of Hg(II) onto MSTT and STT are endothermic, spontaneous and random adsorption process. The regeneration of adsorbents and high Hg(II) adsorption efficiencies in the presence of other metal ions will endow the prepared MSTT and STT with a promise for efficient Hg(II) adsorption for environmental remediation.

A novel microcapsule-type thermal latent curing agent with a double-shell structure was successfully fabricated. 1-Benzyl-2-methylimidazole (1B2MZ) was encapsulated by poly(methyl methacrylate-n-butyl acrylate) (PMMA/BA) using the solvent evaporation method, which served as the primary microcapsules (PMCs) to be deposited by polydopamine (PDA). Various glass transition temperatures (Tg, from 116.7 to 57.2 °C) and thermal properties of shell material PMMA/BA were obtained by tuning the mass ratio of BA to MMA monomer. PMMA/BA with 20 wt% of BA ratio was selected as the shell of PMCs for its appropriate Tg (92.33 °C) and relatively good thermal resistance. (Decomposition temperature was 222.83 °C.) The obtained PMCs and the double-shell microcapsules (DMCs) had good spherical shape, and the chemical structure of DMCs was confirmed by Fourier transform infrared spectra. Thermogravimetric analysis indicated that the core contents of PMCs and DMCs were 11.95 and 11.37%, respectively. After being coated by PDA, the solvent resistances of microcapsules in weak-polar (toluene) and high-polar (dichloromethane, DCM and acetone) solvents were significantly improved. When storing at room temperature for more than 4 months, the mixture of DMCs and the diluted epoxy could be cured at 120 °C for 1 h.

Epoxy resins are widely used due to their excellent physical and mechanical properties; however, their recycle and reprocessing remain challenging up to now. This problem may be solved by incorpora...